Iron bridge



'hir

NTTED sTATns T errno.

J. P. FISHER, OF ROCHESTER, NElV YORK.

IRON BRIDGE.

Specification of Letters Patent No. 28,845, dated June 26, 1860.

structed according to my invention. Fig. 2 is an inverted plan of thesame. Fig. 3 is a transverse section of the same. Fig. l

is an inverted plan view exhibiting the Inanner of applying the lowertension braces of each truss frame.

Similar letters of reference indicate cor responding parts in theseveral ligures.

My invention consists in a certain construction of a bridge of a castand wrought iron and wire rope whereby the truss and suspensionprinciples are combined in an advantageous manner, and a bridge of greatstrength and stiffness is obtained with extreme lightness.

To enable others skilled in the art to make and use my invention I willproceed to describe its construction and operation.

A, A, are the sections of the lower chord of the truss frames which formthe sides of the bridge, one for each panel made of cast iron of anarched longitudinal form and of any suitable transverse sectional formand with an upright dovetail groove c, in each end as shown in Fig. 2,to receive onehalf of the'lower part b, of one of the upright cast ironposts B, B, such part b, being made of double dovetail form in itshorizontal section as shown in Fig. 2, where the lower end of one of theposts is left exposed, and a shoulder being formed above the dovetailportion b, to rest upon the sections A, A. C, C, are the sections of thetop chord of the truss, made of cast iron each of the length of a singlepanel or of two or more panels, made of bridge form in the transversesection, to fit over the tops of the posts B, B, as shown in Fig. 3.

cl, d, are string pieces of flat bar iron fitted to the interior of thesections C, O, of the top chord on the top of the posts. The posts B, B,are each cast with a wrought iron rod running right through andprojecting from its ends and the projecting parts e, j", of these rodsare screwed to receive at their ends nuts g, z.. The lower projectingparts c, of the said rods are each fitted with a plate c', large enoughto lap some distance under the bottom of the seg ments A, A, all aroundthe portions of the posts; and above the top of each post a cast ironsaddle j, is fitted over the top chord and the upper parts f, f, of thepost passes through the top chord and saddle. The nuts g, and la., serveto hold the parts of the truss together vertically and they are heldtogether. longitudinally or horizontally by the dovetails b, on theposts, but the parts are further secured by oblique tension braces lc,7c, of wire rope of which there are four to each panel two of which areconnected with each post by passing through eyes Z, Z, provided in thepost to receive'.

them. The four tension braces of each panel are connected together by ascrew E, iitted with a nut fm, and a swivel piece a, t-he two upperbraces passing through eyes provided on the nut and the two lower onesthrough eyes provided on the swivel piece which is so attached to thescrew that the latter may turn freely within it but may have nolongitudinal movement independent of it. By turning the screw E, allfour braces are tightened up together and a uniform strain is broughtupon each one. Besides these tension braces there are oblique braces w,w, of wrought or cast iron applied between the posts and the top chord,to stiffen the top chord in every panel of the truss. At each end of thetruss instead of one of the sections A, there is a short section F,iitted to the end post, with a dovetail and secured by a nut g, andplate c', as before described said sections being intended to rest onthe abutments.

G, G, are the transverse girders which support the floor P, of thebridge made of cast iron iitted to the sections A, of each truss frameat the center of each panel lapping both over and under the saidsections and being secured by screw bolts p, p, passing through them.These girders are arched at their bot-toms and tend to keep the sidetruss frames at the proper distance apart.

H, I-I, are tension braces applied to the truss frames under each panelof the lower chord consisting each of one or more lengths of wire ropepassed one or more times back and forth around two adjacent posts andthe downwardly projecting extremities of the sections A, A, or A, F,which fit to the farthest sides of the said posts as shown in Fig. 4L,and having their ends spliced or otherwise secured together. Thedownwardly projecting extremities of the sections A, A and F, aregrooved as shown at g, g, in Figs. l and 2 to receive the rope andprevent it slipping out of its place. Between that half of each tensionbrace H, which passes on the outer side of the sections A, A, or A, F,and the half which passes on the inner side thereof there is inserted ascrew r, fitted with a nut s, in opposite sides of which there areeither eyes 5, 5, or notches for the two sides of the braces to passthrough. By using this screw as a lever the two halves of the brace maybe twisted once or more times around each other as shown in Figs. 2 andt, and so caused to draw the lower parts of the sections very tightlytogether and when they are drawn as tight as is desirable by this means,one end of the said screw is placed in a recess provided for it in thebottom of its respective section A, of the chord, and the screw turnedlike a jackscrew by applying a wrench at the other end to tighten up thebrace still further by giving it a downward flexure. The screws r, r,besides serving to tighten up the braces H, serve when their ends areinserted in the recesses provided for them in the sections A, to securethe proper tension of the braces. These braces H, counteract thetendency of the load to elongate the' lower portion of the chord.

I, I, are tension braces, precisely like H, H, applied to the floorgirders, passing around the ends of the said girders and eX- tendingacross the arches thereof as shown in Fig. 8 tightened up by means ofscrews t, and nuts u, applied and operating precisely like those r, s,the ends of the said screws resting when the braces are tight inrecesses provided for them in the bottoms of the girders.

J, J, are diagonal tension braces made of wire rope substantially likeH, H and I, I, passing around the downwardly projecting grooved parts g,g, of the sections A, A, and A, F, from one side to the other obliquelyto the sides of the truss and crossing each other near where they alsocross the braces I, I. These braces are represented without separatetightening screws but are connected with each other and with the bracesI, I,

by rings o', o, in such a. manner that by screwin up the screws t, t,against the girders Gr, the said braces are tightened up in a similarmanner to I, I.

K, L, M, are double tension braces applied at different elevations toeach end o each truss frame and anchored in the ground. The braces K,and L, are tightened by screws Q, nuts N, and swivel pieces O, like thescrews nuts and swivel pieces E, and m, before described, the brace K,passing through eyes in the swivel pieces and the brace L, through eyesin the sides of the nuts, and the tightening of the braces beingeffected by turning the screws to force apart the swivel pieces andnuts.

In this construction of bridge the truss frames are self sustainingwithout any of the tension braces which serve to draw up all the partsof the truss close together and to counteract any strain on the trussand are so applied that the heavier the load the tighter will they drawthe parts of the truss together and the stiffer will be the bridge.

What I claim as my invention and desire to secure by Letters Patent isl.Combining the posts and the sections A, A and F, of? the lower chord ofthe truss by means of the double dovetail lower portions of the posts,the dovetail grooves in the ends of the said sections the shoulder andthe screws e, on the posts and the plates z', z', and nuts g, g, thewhole applied and operating substantially as herein set forth.

2. In combination with the sections A, and C, posts B, saddles j,connected and secured together as described I claim the transversegirders G, and the tension braces H, I and J applied and arrangedrelatively to each other and to the said sections and postssubstantially as herein specified.

3. The tightening of the wire rope braces H, H, and I, or any other wirerope tension braces of a bridge by means of screws and nuts r, s, and t,u, constructed and applied substantially as herein described that 1s tosay so that the screws tighten the braces by twisting their partstogether and hold them tight and serve to tighten them further bybearing in recesses in a rigid part of the structure substantially asherein specified.

J. P. FISHER.

IVitnesses:

Houmt H. WooDwARD, JOHN PHILIP BECK.

